1. Field of the Invention
The present invention relates to a chemical heat pump.
2. Description of the Related Art
From the viewpoint of efficient resource and energy use, there is a growing need to realize a technology for storing waste heat generated in a factory, or the like for a prolonged period and reusing the stored heat at any time. Chemical heat pumps (heat pumps using a chemical heat storage system) have been devised as one of the approaches for realizing this technology (see, for example, PTLs 1 and 2).
Each of the chemical heat pumps disclosed in the cited literature includes a “reaction section containing a heat storage material”, a “condensing section containing water vapor and water and enabling a phase transition between the water vapor and the water”, a “connecting section connecting the reaction section and the condensing section”, a “valve adapted to open or close the connecting section”, and a “first fluid passage in which heat exchange is performed between a fluid flowing therein and the heat storage material”. This “heat storage material” has: “a property of dissipating heat while being converted into a hydrate by an exothermic reaction with water vapor” (first property); and “a property of storing heat while releasing water vapor and thus being dehydrated by an endothermic reaction of the hydrate caused by receiving external heat” (second property).
In the heat storage mode of the chemical heat pump, a high-temperature gas is introduced into the first fluid passage in a state where the valve is open. When the high-temperature gas flowing in the first flow channel passes a position at which the heat exchange is performed, the hydrate of the heat storage material in the reaction section receives heat from the high-temperature gas. Thus, an endothermic reaction of the hydrate occurs according to the “second property”, so that the hydrate dehydrates to be converted into the heat storage material itself (=dehydrated material), and the temperature of the heat storage material increases (that is, the heat storage material stores heat). Water vapor (gas) generated by the dehydration flows to the condensing section from the reaction section through the connecting section. The water vapor that has reached the condensing section is converted into water (liquid) by phase transition (condensation), and the water is stored in the condensing section. The high-temperature gas is deprived of heat by the endothermic reaction. Consequently, the temperature of the gas (exhaust gas) discharged from the first fluid passage is reduced. Thus, in the heat storage mode, some of the heat of a high-temperature gas is stored in the heat storage material (dehydrated material) by introducing the high-temperature gas into the first fluid passage in a state where the valve is open.
To hold the heat stored in the heat storage material (=dehydrated material), the valve is closed. Since water vapor generated from the water in the condensing section cannot flow to the reaction section when the valve is closed, an “exothermic reaction” does not occur between the “heat storage material in the reaction section” and the “water vapor”. Hence, the heat storage material in the reaction section is kept in a “dehydrated material” state. Consequently, the heat stored in the heat storage material (=dehydrated material) can be held in the heat storage material over a desired period in which the valve is kept closed.
In the heat dissipation mode, a low-temperature gas (for example, a gas at room temperature) is introduced into the first fluid passage in a state where the valve is open. Since the valve is open, the water vapor generated by phase transition (evaporation) of the water in the condensing section flows to the reaction section from the condensing section. Consequently, an “exothermic reaction” occurs between of the “heat storage material (=dehydrated material in the reaction section” and the “water vapor” according to the “first property”, so that the heat storage material dissipates heat and is converted into a hydrate. When the low-temperature gas flowing in the first fluid flow channel passes a position at which the heat exchange is performed, the “low-temperature gas” receives the heat generated by the heat dissipation of the heat storage material.
Consequently, the temperature of the gas discharged from the first fluid passage is increased. Thus, in the heat dissipation mode, a high-temperature gas can be taken out by introducing a low-temperature gas into the first fluid passage in a state where the valve is open. In other words, the heat stored in the heat storage material (=dehydrated material) can be reused.